INTEGRAL and Swift observations of IGR J19294+1816 in outburst

Abstract

Context. IGR J19294+1816 was discovered by INT EGRAL in 2009 during a bright X-ray outburst and was classified as a possible Be X-ray binary or supergiant fast X-ray transient. Aims. On 2010 October 28, the source displayed a second X-ray outburst and a two months-long monitoring with Swift was carried out to follow the evolution of the source X-ray flux during the event.Methods. We report on the INT EGRAL and Swift observations of the second X-ray outburst observed from IGR J19294+1816. Results. We detected pulsations in the X-ray emission from the source at ∼12.5 s up to 50 keV. The source X-ray flux decreased smoothly during the two months of observation, displaying only marginal spectral changes. Owing to the relatively rapid decay of the source X-ray flux, no significant variations of the source spin period across the event could be measured. This prevented a firm confirmation of the previously suggested orbital period of the source at 117 d. This periodicity was also searched for in archival Swift /BAT data. We detected a marginally significant peak in the periodogram and determined the best period at 116.2±0.6 days (estimated chance probability of a spurious detection 1%).Conclusions. The smooth decline of the source X-ray flux across the two months of observations after the onset of the second outburst, together with its relatively low value of the spin period and the absence of remarkable changes in the spectral parameters (i.e., the absorption column density), suggests that IGR J19294+1816 is most likely another member of the Be X-ray binaries discovered by INT EGRAL and not a supergiant fast X-ray transient.

Progress on the Knowledge of Neutron Stars and their Magnetic Fields with XMM-Newton

“…The sources underwent a bright X-ray flare that started about 5 ks after the beginning of the observation and lasted for ∼15 ks. This observation provides convincing evidence that the flare was produced by the accretion of matter from a massive clump onto the compact object hosted in this system [25].…”

Timing and Spectral Study of IGR J19294+1816 with the RXTE: The Discovery of Cyclotron Features

“…Further the spectral parameters during the two months spanned by the Swift observations, along with its low spin period, seem to confirm that the source is a Be/X-ray transient (Bozzo et al 2011). In this paper, we report the timing and spectral properties of the source during the decay phase of the 2009 and 2010 outburst as observed by the RXTE/PCA.…”

High-mass X-ray binaries in the Milky Way

“…The relation between orbital and pulsation periods, as well as transient nature, lead to the identification of this source as a Be binary system with the X-ray pulsar. The source broadband spectrum could be well fitted by a cut-off power law with photoabsorption: photon index 0.4 ± 0.3, Ecut = 8.0 +1.2 1.0 keV, N H = (3.1 ± 0.7) × 10 22 cm −2 (Bozzo et al, 2011a).…”